FIG. 1 shows a typical electron beam or ion beam system. A vacuum chamber 1 contains a multi-axis motion system 2 which is used to position an object 3, such as a semiconductor wafer, under a beam 4 so that one or more sites of interest on the object 3 may be examined or processed. A column 5 on top of the vacuum chamber 1 provides an electron beam or ion beam. Generally, an electron beam is used to scan, observe, and measure features at sites of interest on the object 3. Focused ion beams (FIB) may be used to observe and repair features. Electron, laser, or ion beams can be used to control processes, such as removal or deposition of material(s), at sites of interest on the object 3. In some designs, two or more columns are used on one vacuum chamber, such as an electron beam system for observing defects and a separate FIB column for repairing defects.
A common arrangement in such motion systems is to have a tilting stage 6 on top of a rotating stage 7, on top of a Y-axis stage 8, on top of an X-axis stage 9. When a large variety of object thicknesses must be managed, a Z-axis of motion stage 10 is also included in the multi-axis motion system 2. The stacked arrangement in such a multi-axis motion system 2 limits accuracy of measurement(s) that can be obtained.
Often stepper motor drives are used to move the stages in their respective axes. A count of steps taken is used to effect approximate navigation. Then, the user must search in X, Y, and Z for each site of interest. After these adjustments are made, the object 3 may be tilted by using the tilting stage 6 to gain better access to lower layers at each site of interest.
Tilting the object 3 without moving the site of interest is not a simple task. Electron beam and FIB systems have limited viewing space. Most motion systems that provide a tilting motion quickly move the site of interest outside the viewing space. This problem is generally due to mechanical tolerances. Sometimes it is due to an inferior arrangement of the axes of motion. It is also a challenge to properly align the axis of beam 4 with the axes of motion in the multi-axis motion system 2.
The system in FIG. 1 often limits the size of object that can be moved, observed, or processed. Generally, a small object, broken from an original full-sized object, is all that can be placed on such a motion system 2. This limits use of the system to analytical tasks, since the broken piece often cannot be returned to the manufacturing line.
Electron, laser, or ion beam columns may be used in conjunction with one or more fixed gas jets 11 to remove or deposit material at each site of interest on an object. While it is possible to refocus the beam 4 over short distances, it is impractical to move gas jets 11.
A more robust motion system is needed. Users need to handle complete objects, without breaking them, and to navigate quickly and accurately to each site of interest. They need to do this when the object 3 has been tilted through an arbitrary angle, to navigate accurately in tilted space without the need for constant adjustment of the electron beam, laser beam, ion beam, or gas jets.